Methods and apparatus for dispersing a fluent material utilizing an electron beam

ABSTRACT

Apparatus for dispersing a fluent material such as a liquid includes a device for discharging a stream of the fluent material and a device for providing energetic electrons such that the electrons impinge on the fluent material to provide a net negative charge on the fluent material in the discharged stream. The fluent material discharged is dispersed at least partially under the influence of the net negative charge so imparted. The electron-supply device includes a chamber separated from the fluid passageway by an electron-permeable membrane, and may also include an electron gun for generating a beam of energetic electrons such that the electron beam passes through the window and impinges on the fluent material. The electrons may impinge on the fluent material as the fluent material is discharged from the device so that the fluid flow carries the charged portions of the fluent material away from the device. The apparatus may be used to atomize liquids even where the liquids are electrically conductive.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 07/438,696, filed Nov. 17, 1989, now U.S. Pat. No.5,093,602.

TECHNICAL FIELD

The present invention relates to methods and apparatus for dispersing afluent material.

BACKGROUND ART

Numerous technical and industrial processes require dispersion of afluent material. One such dispersion process is atomization of a liquidinto droplets. Atomization is employed in industrial processes such ascombustion, chemical treatment of liquids, spray coating and spraypainting. It is ordinarily desirable in dispersion processes such asatomization to produce a fine, uniform dispersion of the fluentmaterial. Thus, in .atomization it is desirable to convert the liquidinto fine droplets, most desirably droplets of substantially uniformsize.

Considerable effort has been devoted heretofore to development ofmethods and apparatus for dispersing fluent materials. For example,mechanical atomizers which operate by forcing a liquid to be atomizedunder high pressure through a fine orifice. Such mechanical atomizersare used in oil burners and as fuel injectors in combustion engines.Other mechanical dispersion devices mix the fluent material to beatomized with a gas flowing at high velocity, so that the fluentmaterial is dispersed by the kinetic effect of the high velocity gas.

A technique known as electrostatic atomization has also been employed.In electrostatic atomization, an electrical charge is applied to thefluent material, typically as the fluent material is discharged from anorifice. Because the various portions of the fluent material bearcharges of the same polarity, various portions of the fluent materialtend to repel one another. This tends to disperse the fluent material.In a rudimentary form of electrostatic atomization, the fluid isdischarged from a nozzle towards a counterelectrode. The nozzle ismaintained at a substantial electrical potential relative to thecounterelectrode. This type of electrostatic atomization is used, forexample, in electrostatic spray painting systems. Electrostaticatomization systems of this nature, however, can apply only a small netcharge to the fluid to be atomized and hence the electrostaticatomization effect is minimal.

U.S. Pat. No. 4,255,777 discloses a different electrostatic atomizationsystem. As taught in the '777 patent, the fluid may be passed between apair of opposed electrodes before discharge through the orifice. Theseopposed electrodes are maintained under differing electrical potentials,so that charges leave one of the electrodes and travel towards theopposite electrode through the fluid. However, the moving fluid tends tocarry the charges downstream, towards the discharge orifice. Generally,the velocity of the fluid is great enough that most all of the chargespass downstream through the orifice and do not reach the oppositeelectrode. Thus, a net charge is injected into the fluid by the actionof the opposed electrodes. Systems according to the '777 patent canapply substantial net charge to the fluid and hence can provide superioratomization.

Systems according to the '777 patent, however, can only be applied wherethe fluid has relatively low electrical conductivity, typically belowabout 1 microSiemens per meter. Where the electrical conductivity of thefluid is substantially greater than 1 microSiemens per meter, it isdifficult to maintain a substantial potential difference between theelectrodes. Although numerous organic liquids can be successfullyatomized by the methods and apparatus of the '777 patent, many otherindustrially significant materials are too conductive and hence cannotbe atomized or dispersed by the methods and apparatus of the '777patent. For example, typical aqueous solutions of inorganic materialsare highly conductive and hence not readily susceptible to electrostaticatomization according to the method of the '777 patent. These conductivesolutions include industrially important material such as water basedpaints and coatings, comestible materials such as beverage extracts andagricultural materials such as aqueous fertilizer solutions, herbicidesolutions and the like.

U.S. Pat. No. 4,618,432 briefly mentions the possibility of using anelectron beam to apply a net charge to a liquid (Column 6, line 19), butoffers no teaching of how to do so. U.S. Pat. Nos. 4,218,410 and4,295,808 and Mahoney et al., Fine Powder Production UsingElectrohydrodynamic Atomization, conference paper, IEEE-IAS 1984 annualmeeting, suggest formation of a metal powder by processes wherein anelectron beam impinges on a mass of metal under high vacuum conditions.U.S. Pat. Nos. 2,737,593 and 3,122,633 refer to treatment of liquids byelectron beams for purposes other than atomization. U.S. Pat. Nos.3,636,673; 4,112,307; 4,663,532 and 4,631,444 are directed to variousstructures employing an electron-permeable membrane, also referred to asan "electron window". A paper by A. Mizuno, Use of an Electron Beam forParticle Charging, IEEE Transactions on Industry Applications, Vol. 26,No. 1 (January/February 1990) discusses the use of electron-beamionization in a precharger for an electrostatic precipitator and theextraction of negative ions and free electrons from the ionization zoneby an applied electric field.

Despite these efforts in the prior art, there has been a substantial,unmet need heretofore for improved methods and apparatus of dispersion.The present invention addresses these needs.

DISCLOSURE OF INVENTION

One aspect of the present invention provides apparatus for dispersing afluent material. The apparatus according to this aspect of the inventionincludes an electron-permeable membrane having a first side and a secondside, and fluent material discharge means for passing fluent material tobe dispersed past the first side of the electron-permeable membrane anddischarging the fluent material. The apparatus further includes electronsupply means for providing free electrons at the second side of themembrane so that the electrons pass through the membrane and enter thefluent material to provide a net negative charge on the fluent materialdischarged by the fluent material discharge means. In operation, thedischarged fluent material is dispersed at least partially under theinfluence of the net negative charge imparted by the electrons enteringthrough the membrane. The electron supply means may include a chamberhaving an interior space on the first side of the membrane, means formaintaining the interior space substantially under a vacuum and meansfor accelerating electrons to form an electron beam within the interiorspace and means for directing electrons in the beam through theelectron-permeable membrane to impinge upon the fluent material.

The fluent material discharge means may include a body defining apassageway having a downstream end and a discharge orifice at thedownstream end of the passageway, and means for advancing the fluentmaterial through the passageway to the discharge orifice so that thefluent material is discharged from the discharge orifice. Theelectron-permeable membrane preferably is disposed adjacent thedischarge orifice so that the electrons passing through the membranewill impinge on the fluent concomitantly with passage of the fluentmaterial through the discharge orifice.

Use of the electron-permeable membrane permits operation of electronsupply apparatus such as the electron beam generating apparatus underhigh vacuum conditions, even though the fluent material is atatmospheric or superatmospheric pressures. This allows use of electronsupply apparatus such as electron beam generating equipment and plasmagenerating equipment which operate most efficiently under lowsubatmospheric pressures. Moreover, introduction of electrons throughthe electron-permeable membrane avoids the need to maintain a potentialdifference across the fluent material and thus facilitates introductionof a net charge into the fluent material even where the fluent materialis electrically conductive.

Because the electrons are introduced into the fluent material as thefluent material passes downstream through the discharge orifice, thedownstream motion of the material tends to carry the electricallycharged portions of the fluent material away from the apparatus beforethe charge on these portions of the fluent material can dissipate byconduction through the fluent material to the apparatus.

The means for passing the fluent material may include means forprojecting the fluent material in a stream surrounding a discharge axisand moving generally parallel to the discharge axis, and the electronsupply means may include means for directing electrons into the streamadjacent to the discharge axis. For example, the electron-permeablemembrane may be disposed at an injection location upstream of thedischarge orifice, and the electron supply means may include electronbeam means for directing an electron beam through the membranesubstantially in the axial direction from the injection location towardsthe discharge orifice. The means for passing fluent material may includemeans for directing fluent material into rotational flow about thedischarge axis so as to form a vortex adjacent the discharge axis, andthe electron beam means may include means for directing the electronbeam into the vortex. Alternatively, the electron-permeable membrane mayencircle the discharge axis and may extend downstream of the dischargeorifice.

According to a further aspect of the invention, the apparatus mayinclude means for decreasing the static pressure of the fluent materialadjacent the electron-permeable membrane. Thus, the passageway mayinclude a venturi section to decrease the pressure of the fluentmaterial. The electron-permeable membrane may be disposed adjacent tothis section. Apparatus according to this aspect of the invention isparticularly useful where the fluent material includes a gaseous phase.In this case, the density of the gaseous phase decreases with the staticpressure. Electrons passing through the membrane encounter lessresistance to penetration of, and incorporation into, the fluentmaterial, and dissipation of the electrons through paths of conductionthrough the fluent material are disrupted. In the case of a liquid, thefluent material may be passed through a mechanical pre-atomizer toobtain a gaseous phase prior to injection of the electrons. Theelectron-permeable membrane may be disposed either parallel or traverseto the axis of the venturi section.

Since the injection of electrons into the fluent material may produceX-rays or other undesirable electromagnetic radiation, the apparatus mayinclude means for blocking transmission of such radiation from thevicinity of the membrane to the extension of the device. The blockingmeans may include one or more baffles. The baffles may constitutebounding walls of the passageway for the material and these walls maydefine a tortuous-path section. This section may be located downstreamof the membrane but upstream from the discharge orifice to interceptradiation travelling axially along the passageway prior to its emissionfrom the downstream end of the passageway.

Collisions between free electrons and molecules and/or atoms of thefluent material, and/or atmospheric or other gases, are believed toproduce both positive and negative ions. Extraction of the positive ions(cations) from the fluent material enhances the total net negativecharge carried by the material. The apparatus, therefore, may includeone or more electrodes disposed adjacent the electron-permeable membraneand means for maintaining each such electrode at a relatively negativevoltage potential, i.e., at a potential which is negative with respectto the other surfaces in the vicinity of the membrane. The electrodesthus attract cations from the fluent material, and promote applicationof a net negative change on the fluent material.

The electron-permeable membrane may comprise a film formed from boronnitride (B₄ NH). The thickness of this film preferably ranges from abouttwo to about three microns. Because of boron nitride's lowelectron-absorption characteristics, the electron supply means maycomprise an electron gun having an electron acceleration potential ofabout 30 kV or less. The ability to use such a relatively low-energyelectron source provides significant advantages in that it minimizesproduction of unwanted X-ray radiation and requires only simple,low-cost power supplies such as those normally used for cathode-raytubes.

In another aspect, the present invention provides apparatus fordispersing a fluent material in which the degree of dispersion varieswith time. This variation can be in synchronization to the operatingcycle of a device receiving the dispersed material. An apparatusaccording to this aspect of the invention includes means for supplyingthe material, means for injecting electrons into the material so thatthe material is dispersed at least partially because of the charge ofthe electrons, and means for varying in synchronization to the operatingcycle of a device receiving the material the quantity of the electronsinjected into the material to thereby vary with time the extent of thedispersion in synchronization with this cycle. The means for injectingthe electrons may comprise an electron gun, and the means for varyingthe quantity of electrons injected into the material may comprise meansfor varying the intensity of an electron beam produced by the gun. Thedevice receiving the dispersed material may be an internal combustionengine, such as a gasoline or diesel engine.

Further aspects of the present invention provide methods of dispersing afluent material. In such methods, the fluent material to be dispersedmay be moved past a first side of an electron-permeable membrane anddischarged, whereas electrons may be supplied on the second, oppositeside of the membrane so that the electrons pass through the membrane andenter the fluent material so as to provide a net charge on thedischarged fluent material. The fluent material may be a liquid and theliquid may be atomized at least partially under the influence of the netnegative charge imparted by the electrons. Alternatively, the fluentmaterial may include a gaseous phase and a solid or liquid phase inadmixture with the gaseous phase. The fluent material may be eitherelectrically conductive or nonconductive. As discussed above inconnection with the apparatus, the electrons may be introduced into thefluent material as the fluent material travels through a passageway andexits from a discharge orifice.

The fluent material may be brought to a reduced static pressure aselectrons are injected into the fluent material. Thus, the fluentmaterial may be passed through a venturi, with the electron-permeablemembrane disposed adjacent the venturi, and the electrons may besupplied to the second side of the membrane concomitantly with thepassage of the material through the venturi. X-rays and otherelectromagnetic radiation produced upon injection of electrons into thefluent material may be blocked so that such radiation cannot exit fromthe apparatus. Thus, radiation travelling axially along the passagewaymay be intercepted prior to exiting the discharge orifice of thedownstream end. The fluent material may be directed past one or moreelectrodes adjacent the first side of the electron-permeable membraneand a relatively negative electrical potential may be applied to suchelectrodes to attract positively charged particles. The electrons may besupplied by an electron gun which accelerates the electrons through avoltage potential of less than 30 kV and through an electron-permeablemembrane consisting essentially of boron nitride.

In accordance with a further method of the present invention, the extentof dispersion of the fluent material is varied with time. This variationmay be in synchronization to the operating cycle of a device receivingthe dispersed material. In accordance with this aspect of the invention,the fluent material is injected with electrons, and the quantity ofelectrons is varied in synchronization with the operating cycle of adevice receiving the material to thereby vary with time the degree ofdispersion in synchronization with this cycle. The injected electronsmay be supplied by an electron gun whose beam intensity varies with thiscycle.

Other objects, features and advantages of the present invention will bemore readily apparent from the detailed description of the preferredembodiments set forth below taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view of apparatus in accordance with oneembodiment of the present invention.

FIG. 2 is a sectional view taken along lines 2--2 in FIG. 1, withportions of the apparatus removed for clarity of illustration.

FIG. 3 is a fragmentary, idealized sectional view depicting a portion ofthe apparatus of FIG. 1 on an enlarged scale.

FIGS. 4, 5 and 6 are views similar to FIG. 3 but depicting apparatusaccording to additional embodiments of apparatus according to theinvention.

FIG. 7 is a schematic sectional view of apparatus in accordance withanother embodiment of the present invention.

FIG. 8 is a fragmentary, sectional view depicting additional apparatusaccording to the invention.

FIG. 9 is a schematic sectional view of apparatus in accordance withanother embodiment of the present invention.

FIG. 10 is a schematic sectional view depicting a variation of theapparatus illustrated in FIG. 9.

FIG. 11 is a schematic representation of apparatus in accordance withanother embodiment of the invention.

FIG. 12 is a diagram illustrating the potential gradient extendingthrough the electron window of the embodiment of FIG. 9.

MODES FOR CARRYING OUT THE INVENTION

Apparatus in accordance with one embodiment of the present inventionincludes a body 10 incorporating a central portion 12 and a coverportion 14 attached to the body portion by threads 16. The body portionand cover portion are substantially symmetrical about an axis 18. Thebody portion and cover portion cooperatively define a cylindrical space20 and a general conical space 22 leading to a cylindrical dischargeorifice 24. Spaces 20 and 22 and discharge orifice 24 are substantiallyconcentric with one another and are centered on axis 18. Spaces 20 and22 and discharge orifice 24 cooperatively define a continuous passageway26, the discharge opening 24 being disposed at a downstream end of thepassageway. An inlet opening 28 is provided at the upstream end of thepassageway, and communicates with cylindrical space 20. A set of vanes30 project into the conical space 22 and hence into passageway 26 fromcover element 14. As best seen in FIG. 2, vanes 30 are disposed atlocations spaced apart circumferentially about axis 18. The vanes 30extend radially with respect to axis 18 and are also curved in a uniformcircumferential direction. Thus, as seen in FIG. 2, the radially inwardend 32 of each vane is disposed slightly clockwise of the radiallyoutward end 34 of the same vane, but the vane curves in theanticlockwise circumferential direction with respect to axis 18. A pump29 is connected to a tank or other source 31 of a liquid to be atomized,and to the inlet opening 28 such that the pump 29 can force a liquidfrom source 31 into the inlet opening 28.

The central portion 12 of body 10 has a bore 36 coaxial with centralaxis 18 and extending through the central portion to a circular beaminlet opening 38 on axis 18. Beam inlet opening 38 is covered by anelectron-permeable membrane 40, so that the membrane 40 separates thespace within bore 36 from passageway 26, and so that the membrane formsa wall of the passageway. Membrane 40 is bonded to the central portion12 of the body around the entire periphery of beam inlet opening 40, sothat the membrane and body cooperatively provide air, gas and liquidimpermeable barrier. A first side of membrane 40 faces into thepassageway, and a second side of membrane 40 faces away from thepassageway, into bore 36. Membrane 40 extends substantiallyperpendicularly to axis 18 and the first side of membrane 40 facesdownstream towards discharge orifice 24. Membrane 40 may be formed fromboron nitride, beryllium or other known, electron-permeable materials.Most desirably, the membrane 40 has the minimum thickness required towithstand the pressures encountered in service. To permit use of thethinnest possible membranes, it is desirable to minimize the dimensionsof the membrane and hence to minimize the dimensions of opening 38.Where membrane 40 is formed from boron nitride, its thickness may be onthe order of about 2 micrometers to about 10 micrometers, and mosttypically about 3 micrometers. Preferably, the diameter of beam inletopening 38 is about 2 mm to about 10 mm, and most typically about 3 mm.Where the opening 38 is not circular, the smallest dimension of the beaminlet opening may be about 2 mm to about 10 mm, and desirably about 6mm. These preferred ranges apply with respect to unreinforced boronnitride membranes. Membrane 40 may be reinforced by a grid or mesh ofreinforcing elements (not shown) covering one or both surfaces of themembrane. In this case, the beam inlet opening may have greaterdimensions, or the membrane 40 may be thinner than specified above.

The apparatus further includes an electron gun assembly 41 having anenclosed electron accelerating tube 42, of which only a portion is shownin FIG. 1. Accelerating tube 42 is connected to the central portion 12of body 10 such that the interior space 44 within accelerating tube 42is in communication with the interior bore 36 of body 12. A high vacuumseal 46 is provided at the juncture of tube 42 and body 12, such thatthe interior space 44 and bore 36 are effectively isolated from thesurrounding atmosphere. When tube 44 is first assembled with body 12,the interior space 44 and bore 36 are evacuated by a conventional vacuumpump 48. After evacuation, the connection between the pump 48 and theinterior space may be broken, as by a valve 50 and the pump may beremoved. A chemical substance 52 adapted to react with and consume anyatmospheric gases present within space 44 is also provided inside ofspace 44. Such chemical substances are commonly referred to as "getters"and are well known in the electron tube art. Where the seal 46 betweenthe tube and body is particularly effective, the getter may be omitted.Alternatively, where there is appreciable leakage into the interiorspace 44, the vacuum pump 48 may remain connected to the space.

Desirably, the interior space within the acceleration tube and bore aremaintained substantially at a vacuum, i.e., at an internal absolutepressure less than about 10⁻⁶ Torr and desirably less than about 10⁻⁷Torr. Electron gun assembly 41 is equipped with a conventional cathode54 and conventional electron accelerating devices such as conductiverings 56 spaced along the length of tube 42. Further, the electron gunassembly includes an electron beam focus device such as the coil 58schematically depicted in FIG. 1. This device provides a wide focus tothe beam such that an even density of electrons appears across the fulldimensions of opening 38. The elements of the electron gun assembly areconnected to a conventional electrical power source 60 of the typecommonly employed for electron beam operations. Power source 60 isarranged to apply a substantial negative electrical potential to cathode54, and to apply appropriate electrical potentials to rings 56 so thatelectrons will be discharged from cathode 54 and accelerated away fromthe cathode by electrostatic potentials applied through rings 56. Thepower source is arranged to energize coil 58 to provide a focusingmagnetic field so as to focus these accelerated electrons into arelatively narrow beam directed substantially along axis 18.

A method according to one embodiment of the invention utilizes theapparatus discussed above with reference to FIGS. 1-3. Pump 29 isactuated to draw a liquid from liquid source 31 and force the liquiddownstream through passageway 26, and hence through discharge orifice24. The liquid may be an electrically conductive liquid such as anaqueous solution of an inorganic salt, or else may be a substantiallynonconductive liquid such as a liquid hydrocarbon. As used in thisdisclosure with reference to a liquid, the term "conductive" meanshaving an electrical resistivity of less than about 10⁶ ohm-meter. Manyconductive liquids have still lower resistivities, typically as low asabout 1 ohm-meter or less. The term "non-conductive," as used withreference to a liquid, means having an electrical resistivity greaterthan about 10⁶ ohm-meter, and typically greater than about 10⁸ohm-meter.

The liquid passing downstream through passageway 26 encounters vanes 30as the liquid traverses the conical portion 22 of the passageway andapproaches the discharge orifice 24. Vanes 30 impart a swirling,rotational motion about axis 18 to the liquid. As the swirling liquid 62enters discharge orifice 24, it forms a whirling vortex about axis 18,and hence forms a hollow vortex space or gap 64 (FIG. 3) immediatelyaround the axis 18. The liquid passing through the discharge orifice isprojected downstream from the orifice as a whirling stream 66 movinggenerally parallel to axis 18.

While the pump 29 is in operation, electron gun assembly 41 and powersource 60 are actuated to provide a beam 68 of electrons. The beam 68 isdirected by focusing coil 58 through electron-permeable membrane 40 andhence into passageway 26. The beam enters the passageway through themembrane 40 at the beam inlet opening 38. The electrons in beam 68 passdownstream from the beam inlet opening generally parallel to axis 18,towards discharge orifice 24. As best appreciated with reference to FIG.3, the electrons in beam 68 impinge upon the liquid 62 as the liquidpasses through orifice 24. The gap or space 64 created by the swirlingvortex allows at least a portion of the beam 68 to penetrate downstreaminto orifice 24 and, depending upon the extent of the vortex, beyond thedownstream edge 70 of the orifice. As the space 64 within the vortex isfilled with vapors of the liquid and/or atmospheric gases, there may besome interaction between the beam and the gases in the hollow space.However, this interaction is relatively minor, so that the major portionof the electrons in beam 68 impinge upon the liquid 62. As the electronbeam 68 passes through membrane 40 and into vortex space 64 and thestream 66, the electron beam encounters gasses within the vortex spaceand creates negatively charged ions, i.e., gas atoms and/or moleculesincorporating one or more additional electrons. The beam spreads awayfrom the axis 18 under the influence of mutual repulsion between thenegatively charged electrons and ions. Thus, the beam spreads radiallyoutwardly, away from axis 18 into the body of the stream 66. As theelectrons and ions impinge upon the liquid, the liquid assumes a netnegative charge. Although the present invention is not limited by anytheory of operation, it is believed that some or all of the freeelectrons in the original beam passing through the membrane may becomeattached to atoms or molecules and form negative ions before theelectron impinges on the fluid stream. However, regardless of whetherthe electrons are free or attached as ions, the result is the same, inthat the electrons pass into the fluid stream. Each negative ion whichpasses into the fluid stream carries one or more extra electrons intothe fluid with it. As the negatively charged portions of the liquid tendto repel one another, the liquid stream 66 fragments into droplets 72,thus atomizing the liquid. The atomization process may be assisted bymechanical action of the liquid passing through the orifice. Thus, thestream 62 will tend to fragment to some extent even in the absence ofthe electron beam. However, the atomization process is materiallyenhanced by the negative charges applied by the electron beam.

Where the liquid 62 is conductive, the charge applied to the liquid bythe electron beam may be dissipated to some extent by conduction. Thus,the charge applied by the electron beam tends to flow through the liquidto the nearest available ground. Preferably, the nozzle body 10 isformed from an electrically insulating material or else substantiallyelectrically isolated from ground. Liquid source 31 and pump 29 maythemselves be isolated from an electrical ground, so that as the systemoperates, the liquid source, the pump, the conduits connecting them tothe inlet opening 28 and the liquid within them assume a net negativecharge. Alternatively, the conduits connecting the pump 29 to the inletopening may be formed from an insulating material, and may be relativelysmall across section and relatively substantial in length, so that theonly electrical pathway from the nozzle to the pump is a high impedancepathway through the liquid column in the conduits. This arrangementminimizes current flow and hence charge dissipation, even where the pump29 is grounded.

Even where there is an available electrical path from the liquid toground, as where the nozzle body itself is conductive and grounded, orwhere there is a high conductivity pathway through the liquid conduits,not all of the charge applied by the electron beam will be dissipated.The velocity of charges in a typical conductive liquid is finite, and isconsiderably less than a velocity of light. In a typical conductiveliquid, charges are transferred by diffusion of ions through the liquidunder the influence of the voltage gradient or prevailing electricfield. Such diffusion proceeds at a rapid but finite speed. In thepreferred embodiments of the present invention, the charges are injectedinto the liquid just as the liquid passes through the discharge orifice.At this point, the liquid is passing downstream, away from body 10 at asubstantial velocity. If the downstream velocity of the liquid exceedsthe charge velocity in the liquid, the charges will move downstream withthe exiting liquid stream, away from the body and away from thedischarge orifice 24. Even where body 10 is grounded and electricallyconductive, some or all of the charge applied by the electron beam willremain in the exiting liquid.

The charge remaining in the exiting liquid desirably amounts to at leastabout 3×10⁻³ coulombs per liter of fluid discharged and higher levels ofcharge, on the order of at least about 4×10⁻³ coulombs per liter or atleast about 5×10⁻³ coulombs per liter are more preferred. Thus, for eachml/sec liquid flow through the system, the current of electrons inelectron beam 68 amounts to about 3×10⁻⁶ amperes or more, and preferablyabout 4×10⁻⁶ and most desirably at least about 5×10⁻⁶ amperes. Stillhigher levels of beam current are even more desirable. Desirably, thebeam voltage (the kinetic energy of the electrons in beam 68) amounts toabout 15 kV. Higher energy levels are useful and preferred. However,generation of electron beams at energy levels above about 30 kVgenerally requires more complex equipment incorporating special,expensive high voltage insulation in the power supply. Accordingly.electron beam of voltages within a range of about 15 kV to about 30 kVare most preferred.

The apparatus and methods discussed above may be employed using a widevariety of fluid materials. In particular, both conductive andnon-conductive liquids may be atomized. Substantially the same apparatusand methods can be used to treat fluent materials incorporating a solidphase, such as a fluent powder or a suspension of a solid in a liquid orgas. In this case, the individual particles of the solid may be chargedby exposure to the electron beam, and hence may be dispersed byprocesses including a mutual repulsion of the charged particles.Typically, the shape and size of the passageway 26 in body 10 would beselected to accommodate a flow of the solid particles of materialwithout binding or jamming, and the solid particles of material would befed by an appropriate feeding device such as a vibratory feeder, ram orthe like. Processes according to this aspect of the invention provide adispersion of the solid particle material in the surrounding atmosphere,rather than atomization of a liquid. As used herein, the term "adispersion" and the "dispersing" should be understood broadly, asencompassing both dispersion of a solid particle material andatomization of a liquid material.

The liquid droplets or dispersed solids provided at the downstreamportion of the fluent material stream may be employed in substantiallythe same way as liquid droplets created by conventional nozzles. Thus,liquid droplets resulting from the process may be blended with a gas, asin a combustion process or in creation of a fog, mist or vapor. Thedroplets may also impinge on a solid substrate, such as a workpiece tobe coated with the liquid. The substrate (not shown) may be grounded ormay be maintained at a positive potential relative to ground so as toattract the negatively charged droplets. Likewise, where fluent solidmaterial is dispersed, the same may be applied to a solid substrate, andthe solid substrate may be positively charged to attract the solidparticles.

In the apparatus and methods discussed above, the stream of electricallycharged fluent material passes downstream from the discharge orificeinto the atmosphere. Corona discharge or electrical breakdown of theatmosphere surrounding the stream may cause some dissipation of theelectrical charge on the fluent material hence may limit the chargewhich can be maintained in the stream to produce a dispersion. Tosuppress such a corona discharge, the stream may be surrounded with ablanket of a dielectric gas. Such blanket need only extend downstream toabout the point where the stream becomes substantially dispersed. Asdisclosed in U.S. Pat. No. 4,605,485, the dielectric gaseous stream maybe provided by a separate, annular orifice surrounding the dischargeorifice of an electrostatic atomization device. Conversely, as disclosedin a U.S. Pat. No. 4,630,169, the inert gas blanket may be provided byadding a volatile dielectric liquid to the fluent material to beatomized prior to discharge of the fluent material through the dischargeorifice, so that the dielectric gas blanket is formed by vapors of thevolatile liquid. Either of these approaches may be employed withatomization methods and apparatus according to the present invention.

The measures disclosed in copending, commonly assigned U.S. patentapplication Ser. No. 07/398,151, filed Aug. 24, 1989 may also beemployed. The disclosure of said U.S. patent application Ser. No.07/398,151 is hereby incorporated by reference herein. As disclosed ingreater detail in said '151 application, the charged fluid stream may beprotected from the surrounding atmosphere by a mist, which may be formedfrom the same or a different liquid as incorporated in the principalstream to be atomized. Even a conductive liquid may form a useful mistfor this purpose. Alternatively or additionally, the stream may besurrounded by a vapor formed by heating a portion of the principalliquid to be atomized.

The apparatus according to the present invention typically is operatedto discharge the stream of fluent material to be dispersed into asurrounding atmosphere which is at a moderate subatmospheric pressure ofabout 1 kPa absolute or above, or at about normal atmospheric pressureor above (about 100 kPa absolute). The pressure of the fluent materialwithin passageway 26 will depend upon the factors such as the flow rateof the fluent material, its viscosity or resistance to flow and thedimensions of the passageway and discharge orifice 24. Typically,however, the fluent material is under atmospheric or superatmosphericpressures. As discussed above, the electron-permeable membrane 40effectively isolates the interior space 44 within the electron gunchamber from these high fluid pressures and hence permits accelerationand focusing of the electron beam substantially in a vacuum.

As illustrated diagrammatically in FIG. 4, the vortex opening 64' withinthe swirling mass of fluid 62' may extend downstream to the point wherethe fluid stream 66' breaks into droplets. In this case, the electronbeam 68' may pass downstream within vortex opening 64'. Nonetheless, theelectron beam will impinge upon the fluid in the stream. As theelectrons in the beam and ions incorporating such electrons tend torepel one another, the beam spreads radially outwardly, away from axis18' as it passes downstream, so that the electrons (whether free orion-attached) in the beam will pass radially outwardly, away from axis18' and enters the stream of fluent material. The electrons may enterthe fluent material over a region of the stream extending from upstreamof the downstream edge 70' of the discharge orifice to downstream ofsuch edge. Depending upon the configuration of the stream and of thebeam, the electrons may enter the fluent material entirely downstream ofthe discharge orifice.

As seen in FIG. 5, the electron-permeable membrane 40" need not beplanar as in the embodiments discussed above but may instead incorporatea cylindrical portion 43 protruding downstream through the dischargeorifice 24". Here again, as the electron beam passes downstream withinthe protruding cylindrical portion 43, it will spread radiallyoutwardly, away from the central axis 18". Accordingly, electrons willpass outwardly through this region of the electron-permeable membraneinto the fluid 62".

The apparatus illustrated in FIG. 6 has a generally planarelectron-permeable membrane 40'" similar to the membrane 40 of theapparatus discussed above with reference to FIGS. 1-3. Membrane 40'" ismounted upstream of the discharge orifice 24"'. A secondary ionizationchamber 100 overlies the portion of membrane 40'" on the axis 18'" andprotrudes axially downstream through the discharge orifice 24'". Chamber100 has a cylindrical wall 102 incorporating a nonporous cylindricalsection 104 adjacent membrane 40'" and a porous, electron-permeablemembrane section 106 remote from membrane 40'" and lying adjacent thedownstream end of chamber 100. The downstream end of chamber 100 isclosed by an impermeable plug 108, whereas the upstream end of thechamber is closed by membrane 40'". The interior space 110 withinchamber 100 is filled with a readily ionizable gas such as neon, argon,helium, krypton or xenon, or combinations thereof, under subatmosphericpressure. The porosity of the wall or membrane section 106 is selectedsuch that the membrane is substantially impermeable to liquids and tothe gas within the interior space 110, but substantially permeable tofree electrons having moderate energy levels. Among the materials havingthis property are sintered glasses having a nominal pore size on theorder of about 20 to about 40 Angstroms. Suitable sintered glasses areavailable from Corning Glass Works of Corning, New York under thedesignation Expanded Vycor, Code 7930. In other respects, the embodimentillustrated in FIG. 6 is similar to the apparatus discussed above withreference to FIGS. 1-3. In operation, the electron beam 68'" generatedby the electron gun assembly (not shown) passes through theelectron-permeable membrane 40'" and into the space 110 within secondaryionization chamber 100. As electrons enter the chamber, they ionize thegas within chamber 110, thus converting the gas to a plasma or mixtureof gas ions and free electrons. Also, as free electrons in the electronbeam enter chamber 110, the plasma acquires a net negative charge.Mutual repulsion of the electrons in the plasma forces free electronsout through the membrane or wall 106. As the fluid 62'" passing outthrough discharge orifice 24'" surrounds membrane or wall 106, electronspassing through the membrane enter the fluid as the fluid passes throughthe discharge orifice. Because the membrane 106 is located adjacent thedownstream edge of the discharge orifice, and because the membrane orwall 106 protrudes beyond the downstream edge of the discharge orifice,electrons are introduced into the fluid in the region of the stream atand downstream of the discharge orifice. As in operation of theembodiments discussed above, the electrons introduced into the fluidimpart a net negative charge to the fluid and cause it to disperse intodroplets. The upstream, impermeable wall 104 of the secondary chamberprevents escape of free electrons from the space 110 within thesecondary chamber to the fluid at substantial distances upstream fromthe discharge orifice. As discussed above, introduction of the chargeinto the fluid at the downstream location tends to assure that thecharges will be swept downstream with the moving fluid, and hence willremain in the fluid even when the fluid has substantial conductivity.

FIG. 7 illustrates additional features of the present invention.Electron window 202 comprises a thin film of boron nitride (B₄ NH) whichis disposed on a silicon substrate 203. This film may be deposited onthe substrate through vacuum evaporation, cathode sputtering or similartechniques. A thin film of aluminum 205, which may be deposited on thesubstrate using similar techniques, is disposed on the opposite side ofthe substrate. A hole 204, etched through the aluminum and substratelayers, is disposed in the center of these layers. The outer annularaluminum layer is bond to body 206 through an ionic bond 210 betweenthis body and layer 205.

Body 206 has a bore 209 coaxial with the central axis 200 of the bodyand electron gun 207. A high vacuum seal (not shown) is provided at thejuncture of gun 207 and body 206. The electron gun includes cathode 211,grid 213 and anodes 214. Various voltages are applied to these elementsby power source 215 to cause the emission of an electron beam 212 topass from the cathode, through the partial vacuum within tube 208 andbore 209, and through boron nitride layer 201 of electron window 202 toimpinge upon fluent material (not shown) flowing past and adjacent thislayer. The voltages applied by power source 215 to cathode 211, grid 213and/or anodes 213 are selectively varied with time by power variationunit 216.

A method according to an embodiment of the invention utilizes theapparatus of FIG. 7 to vary with time the quantity of electrons injectedinto the fluent material to thereby vary with time the extent ofdispersion of this material caused by the injected charge. This featureof the invention is particularly useful when the fluent material is aliquid and is discharged into a device having an operating cycle whoseoptimum atomization requirements vary in synchronization with the cycle,e.g., a fuel injector for an internal combustion engine. Power variationunit 216 causes power source 215 to selectively vary the voltage betweencathode 211 and grid 213, in accordance with the dispersion requirementsfor the fluent material, to cause a corresponding variance in theintensity of electron beam 212. The quantity of electrons passingthrough electron window 202 and, therefore, into the fluent material,similarly varies with the variation of voltage between the cathode andgrid of electron gun 207.

Boron nitride layer 201 offers minimal resistance to passage of electronbeam 212 through window 202. As a result, the degree of accelerationimparted to the electrons by gun 207 need not exceed 30 kV in order thata sufficient charge is applied to the fluent material for mostapplications. Power source 215 applies a voltage of 15 to 30 kV betweencathode 211 and anodes 214. Small electron guns applicable to portabletelevisions can function for this purpose.

FIG. 11 illustrates a different electrostatic atomization system,similar to that disclosed in U.S. Pat. No. 4,255,777, the disclosure ofwhich is hereby incorporated by reference herein. Power source 275impresses a voltage differential between central electrode 267 and anopposed electrode 269 within housing 265. Opposed electrode 269 can beaffixed to, or be part of, the forward wall of this housing. Thisvoltage differential causes electrons to leave central electrode 267 andtravel toward opposed electrode 269 through fluid 279. This fluid flowswithin the housing, around central electrode 267 and through dischargeorifice 263. A pump (not shown) advances the fluid from a reservoir(also not shown) through the housing and discharge orifice. Since themoving fluid carries the electrons downstream, toward the dischargeorifice, most of the electrons pass through the orifice and do not reachopposed electrode 269. After exiting through the orifice, the chargedfluid 273 undergoes disruption and atomization. Current returns to thecircuit by collector electrode 271 which, in this case, is the wall of acylinder of an internal combustion engine. Resistor 277 limits theelectrode current in the event of an internal breakdown in the fluid.

Power variation unit 276 controls power source 275 to impart a selected,time-varying voltage between the central and opposed electrodes. In thiscase, this voltage is determined by synchronization unit 291 whichmonitors the operating cycle of the engine and provides asynchronization signal to power variation unit 276 synchronized to thiscycle. Power variation unit 276 causes the amount of charge injectedinto fluid 279 to vary in response to this signal and, therefore, insynchronization to the combustion cycle of the engine. The degree towhich the fluid is atomized after exiting orifice 263, therefore, alsofollows this same synchronized cycle. Since the degree of atomization ofthe fluid is timed to the engine's combustion cycle, an optimum degreeof atomization can be provided to the fluid throughout the cycle. Asused herein, the phrases "degree or extent of atomization" and "degreeor extent of dispersion" refer to the number and average size ofdroplets or particles per unit volume of fluent material. A higherdegree of atomization or dispersal results in more droplets or particlesper unit volume of the material.

FIG. 8 illustrates an embodiment of the invention in which electrodes225 are disposed on central body 217, adjacent electron-permeablemembrane 228, and opposed electrodes 287 are disposed across from theseelectrodes on cover element 219. The other components of the apparatusillustrated in FIG. 8 are the same as that of FIG. 1. Thus, fluentmaterial 231 travels through passageway 229, formed by central body 217and cover element 219, and is discharged through orifice 221. Electronbeam 224 travels through bore 223 and electron-permeable membrane 228into fluent material 231 as the material travels past the outer surfaceof the membrane and through Orifice 221. As discussed above, it isbelieved that when electron beam 224 passes through membrane 228 andinto the vortex space 230, negatively charged ions (anions), i.e., gasatoms and/or molecules incorporating one or more electrons in additionto their normal complement of electrons, are produced. Some of theseions, along with free electrons, impinge upon fluent material 231 toimpart a net negative charge to this material.

Although the present invention is not limited to any theory ofoperation, it is believed that the introduction of free electrons intovortex space 230 also produces positively charged ions (cations), i.e.,gas atoms and/or molecules missing one or more of their normalcomplement of electrons. It is believed that collisions between freeelectrons and neutrally charged atoms and/or molecules result in thecapture of one or more free electrons by these atoms or molecules, insome cases, and in the dislodging of one or more electrons from theseatoms or molecules in other cases. The introduction of atoms ormolecules missing one or more of their electrons (cations) into thefluent material decreases the net negative charge of the material as itexits orifice 221. Electrodes 225 are positioned adjacent the vortexarea to extract cations 227 from the fluent material. Electrode powerunit 289 applies a negative voltage, e.g., approximately -1.5 kV, tothese electrodes with respect to the surrounding elements of theapparatus to attract the positive ions and withdraw them from the vortexregion. Unit 289 holds opposed electrodes 287 at ground potential, or ata slightly positive potential, such that a voltage gradient ismaintained between central body 217 and cover element 219 which pullspositively charged particles toward the central body, away from thevortex, and negatively charged particles in the opposite direction,toward the vortex. This arrangement minimizes the relative effect ofthese cations and increases the overall negative charge applied to thefluent material.

FIG. 9 illustrates yet another embodiment of the present invention.Cylindrical body 233 comprises inlet section 242, venturi section 235and outlet section 244. These sections enclose concentric cylindricalspaces 247, 248 and 249, respectively, about axis 234. The crosssectional area of cylindrical space 247 progressively narrows in thedirection of venturi section 235. The cross sectional area ofcylindrical space 249 also progressively narrows in the direction ofventuri section 235. The cross sectional area of cylindrical space 248is substantially less than that of both cylindrical spaces 247 and 249.

The apparatus illustrated in FIG. 9 further includes an electron gunassembly 243 which provides a beam of electrons throughelectron-permeable membrane 241. This beam penetrates into body 233 atventuri section 235. A pump (not shown) forces fluent material 250through inlet opening 245 and advances this material through cylindricalspace 247 and in the direction of the venturi section. As this materialis forced through the progressively narrowing cylindrical space formedby inlet section 242 and the venturi section, the pressure exerted bythe material substantially decreases in accordance with well knownprinciples. Although the fluent material may be under atmospheric orsuperatmospheric pressures before reaching these sections,subatmospheric pressures can be obtained within these sections. Thisembodiment of the invention takes advantage of these subatmosphericpressures for insertion of electron beam 253 at this point into thefluent material. It is believed that the decreased pressure within theventuri section enhances the degree to which electron beam 253penetrates the fluent material prior to disruption of the beam.

This embodiment is particularly useful for treating fluent materialsincorporating gaseous and solid materials, such as a powder and gassuspension. Although the present invention is not limited to any theoryof operation, it is believed that the use of a venturi at the point ofinjection of free electrons into such fluent material also promotes theproduction of anions and the incorporation of their negative charge intothe material. Positively charged cations 239, which, as explained above,also may be generated from collisions between the fluent material andelectron beam 253, are pulled away from the material by electrodes 237.These electrodes are disposed within venturi section 235 and adjacentto, and on each side of, electron-permeable membrane 241. Electrodepower unit 281 applies a substantially negative voltage to electrodes237 with respect to the surrounding walls of venturi section 235, e.g.,approximately -1.5 kV, to attract positively charged particles andwithdraw them from this region and the fluent material. Electrode powerunit 281 holds opposed electrode 236, disposed on the opposite wall ofthe venturi section, at ground, or at a slightly positive voltage, inorder that a voltage gradient is maintained across the venturi sectionas illustrated in FIG. 12.

This figure shows that the voltage gradient peaks at approximately -1.5kV at or near electron-permeable membrane 241 and then progressivelydrops off, i.e., becomes more positive, extending away from the membranein the direction of the opposite wall of the venturi section and also inthe direction of the internal chamber of the electron gun. The kineticenergy of the electrons is sufficient to overcome this peak negativevoltage and propel them into the venturi section. The electrons then arepulled by the voltage gradient further into this section whilepositively charged cations are pulled back toward electrodes 237 andaway from this section.

The charged fluent material travels from venturi section 235 throughoutlet section 244, tortuous-path section 251 and discharge orifice 252.X-rays, and other electromagnetic radiation caused by collisions betweenelectron beam 253 and the molecules or atoms comprising fluent material250, are intercepted by tortuous-path section 251. This section preventsthe exiting of this radiation through discharge orifice 252 and possiblycausing harm to an operator of the apparatus. Tortuous-path section 251intercepts all optical paths between cylindrical space 249 and orifice252.

A variation of the apparatus of FIG. 9 is shown in FIG. 10. Inletsection 257 encloses cylindrical space 260 within which is disposedcentral body 255. This body encloses cylindrical space 262 which isconcentric, about axis 258, with cylindrical space 260. The crosssectional area of cylindrical space 260 progressively decreases in thedirection of venturi section 261 in a manner similar to that ofcylindrical space 247 of the embodiment illustrated in FIG. 9. The crosssectional area of cylindrical space 264 enclosed by venturi section 261is substantially less than that of cylindrical space 260 and also issubstantially less than that of the cylindrical space of the outletsection (not shown) connected to the opposite side of the venturisection. An electron gun assembly (not shown) provides a beam ofelectrons 256 traveling axially within central body 255. This beam exitselectron-permeable membrane 259 traveling generally in the samedirection as fluent material 258 as this material travels throughventuri section 261. It is believed that injection of the electron beaminto the fluent material in this direction may enhance the degree ofpenetration of the beam into the material at the venturi section and,therefore, the amount of charge carried by the material as it travelsthrough the outlet section and discharge orifice.

Electrodes 246 are disposed within venturi section 261 and on each sideof electron-permeable membrane 259, and opposed electrodes 254 aredisposed on opposite, internal walls of the venturi section downstreamfrom electrodes 246. Electrode power unit 283 applies voltages toelectrodes 246 and 254 of approximately -1.5 kV and ground (or slightlypositive), respectively, such that a voltage gradient similar to thatillustrated in FIG. 12 is maintained within the venturi section. In thesame manner as explained above in connection with FIG. 9, afterovercoming the peak negative voltage in the vicinity ofelectron-permeable membrane 259, electrons are pulled by this gradientinto the venturi section, and positively charged particles are pulled inthe opposite direction out of this section and toward electrodes 246.

The use of a venturi at the point of injection of free electrons intothe fluent material is particularly useful in treating fluent materialshaving a gaseous phase because the density of such materialssignificantly decreases in response to the decreased pressure within theventuri section. This decrease in density enables enhanced penetrationof the electron beam while inhibiting paths of conduction through thefluent material to ground. In order to take advantage of thesebeneficial effects when the fluent material is a fluid, pre-atomizer 285is disposed within inlet section 257, upstream from the venturi section,to impart a gaseous phase to the fluid. The pre-atomizer forces theliquid under pressure through small orifices to provide a coarseatomization to the fluid and a concomitant production of a gaseousphase. The coarsely atomized fluid then is passed through the venturisection where the gaseous phase is enhanced and electrons are injected.

Numerous variations and combinations of the features discussed above canbe utilized without departing from the present invention as defined bythe claims. For example, sources of electrons other than anelectrostatic accelerating gun can be employed. Also, in embodimentsemploying a secondary chamber as discussed above with reference to FIG.6, the porous wall may be so porous that some of the gas within thechamber escapes. In that case, the secondary chamber can be continuallyrefilled with gas. In a variant of this approach, the secondary chambercan be continually refilled with a plasma bearing a net negativepotential supplied by an external plasma generator such as a radiofrequency plasma generator and charged by contact with electrodesmaintained at a high negative potential. In this case, the electron beamand associated beam-generating apparatus may be omitted. Also, inapparatus such as that discussed with reference to FIGS. 5 and 6, wherethe apparatus itself incorporates a solid body defining an internalpassageway within the stream, there is no need to provide the vortexdiscussed above with reference to FIGS. 1-4. Therefore, the fluidpathway need not be equipped with vanes 30 (FIG. 2) or other elementsfor providing rotational movement of the flowing fluid. As these andother variations and combinations of the features discussed above can beutilized, the foregoing description of the preferred embodiment shouldbe taken by way of illustration rather than by way of limitation of theinvention as defined by the claims.

What is claimed is:
 1. A method of dispersing a fluent materialcomprising the steps of:(a) passing a fluent material to be dispersedpast a first side of an electron-permeable membrane and discharging thefluent material; (b) supplying electrons on a second, opposite side ofsaid membrane so that the electrons pass through the membrane and enterthe fluent material so as to provide a net charge on the dischargedfluent material, whereby the discharged fluent material is dispersed atleast partially under the influence of said net charge, the methodfurther comprising the step of removing positively charged particlesfrom said fluent material in the vicinity of the first side of saidmembrane prior to dispersion of said fluent material.
 2. A method asclaimed in claim 1, wherein said step of removing positively chargedparticles includes the step of maintaining an electrode at a relativelynegative electrical potential in the vicinity of said membrane incontact with the fluent material.
 3. A method as claimed in claim 2,wherein said fluent material includes a gaseous phase, the methodfurther comprising the step of maintaining the static pressure of saidfluent material at a subatmospheric pressure as the fluent materialpasses said membrane.
 4. A method of dispersing a fluent materialcomprising the steps of:(a) passing a fluent material to be dispersedpast a first side of an electron-permeable membrane and discharging thefluent material; (b) supplying electrons on a second, opposite side ofsaid membrane so that the electrons pass through the membrane and enterthe fluent material so as to provide a net charge on the dischargedfluent material, whereby the discharged fluent material is dispersed atleast partially under the influence of said net charge, the methodfurther comprising the step of varying the quantity of said electrons atsaid second side with time.
 5. A method as claimed in claim 4, whereinsaid step of supplying electrons comprises forming an electron beam withan electron gun, and wherein said step of varying the quantity of saidelectrons comprises varying with time the quantity of electrons emittedby said gun.
 6. A method as claimed in claim 4, wherein said step ofvarying the quantity of said electrons comprises varying said quantityin synchronization to the operating cycle of a device receiving saiddischarged fluent material.
 7. A method as claimed in claim 6, whereinsaid device is an internal combustion engine.
 8. A method of dispersinga fluent material comprising the steps of:(a) passing a fluent materialto be dispersed past a first side of an electron-permeable membrane anddischarging the fluent material; (b) supplying electrons on a second,opposite side of said membrane so that the electrons pass through themembrane and enter the fluent material so as to provide a net charge onthe discharged fluent material, whereby the discharged fluent materialis dispersed at least partially under the influence of said net charge,wherein said electron-permeable membrane comprises a film formed fromboron nitride, and said step of supplying electrons comprises the stepof accelerating said electrons with an electron gun through a voltagepotential of less than 30 kV.
 9. A method of dispersing a fluentmaterial comprising the steps of:(a) passing a fluent material to bedispersed past a first side of an electron-permeable membrane anddischarging the fluent material; (b) supplying electrons on a second,opposite side of said membrane so that the electrodes pass through themembrane and enter the fluent material so as to provide a net charge onthe discharged fluent material, whereby the discharged fluent materialis dispersed at least partially under the influence of said net charge,wherein said fluent material is a liquid, and wherein said step ofpassing comprises imparting a gaseous phase to said liquid beforepassing said liquid past said electron-permeable membrane.
 10. A methodas claimed in claim 9, wherein said step of imparting comprisesmechanically atomizing said liquid.
 11. A method for dispersing a fluentmaterial, comprising:(a) supplying said material; (b) injectingelectrons into said material so that said material is dispersed at leastpartially because of the charge of said electrons; (c) discharging saidfluent material into a device having an operating cycle; and (d) varyingthe quantity of said electrons injected into said material insynchronization with said operating cycle of said device to thereby varythe extent of said dispersion in synchronization with said operatingcycle of said device.
 12. A method as claimed in claim 11, wherein saiddevice is an internal combustion engine.
 13. A method as claimed inclaim 11, wherein said step of injecting electrons comprises applying anelectrical potential between a pair of opposed electrodes to cause oneof said electrodes to inject electrons into said material under theinfluence of said potential, said step of supplying said fluent materialcomprises passing said material between said electrodes concomitantlywith the injection of said electrons into said material, and said stepof varying the quantity of said electrons comprises varying theelectrical potential between said electrodes.
 14. A method of dispersinga fluent material comprising the steps of:(a) passing a fluent materialto be dispersed past a first side of an electron-permeable membrane anddischarging the fluent material; (b) supplying electrons on a second,opposite side of said membrane so that the electrons pass through themembrane and enter the fluent material so as to provide a net charge onthe discharged fluent material, whereby the discharged fluent materialis dispersed at least partially under the influence of said net charge,the method further comprising the step of blocking the transmission ofx-ray radiation from the vicinity of said electron-permeable membrane.15. Apparatus for dispersing a fluent material comprising:(a) anelectron-permeable membrane having a first side and a second side; (b)fluent material discharge means for passing fluent material to bedispersed past said first side of said electron-permeable membrane anddischarging the fluent material; and (c) electron supply means forproviding free electrons at said second side of said membrane so thatthe electrons pass through said membrane and enter the fluent materialto provide a net negative charge on the fluent material discharged bysaid fluent material discharge means and so that the discharged fluentmaterial is dispersed at least partially under the influence of said netcharge, said fluent material discharge means including a body defining apassageway having a narrow section forming a venturi, and means forforcing the fluent material to flow through said passageway so that thepressure of the fluent material is reduced below the pressure of thefluid in other regions of said passageway as the fluent material passesthrough said section and wherein said electron-permeable membrane isdisposed adjacent said section so that electrons provided by saidelectron supply means enter the fluent material in said section whilesaid fluent material is under reduced pressure.
 16. Apparatus as claimedin claim 15, wherein said electron-permeable membrane is disposedgenerally parallel to the axis of said section.
 17. Apparatus as claimedin claim 15, wherein said electron-permeable membrane is disposedgenerally transverse to the axis of said section.
 18. Apparatus asclaimed in claim 15, wherein said electron supply means includes anelectron gun for directing an electron beam through said membrane intosaid venturi section.
 19. Apparatus for dispersing a fluent materialcomprising:(a) an electron-permeable membrane having a first side and asecond side; (b) fluent material discharge means for passing fluentmaterial to be dispersed past said first side of said electron-permeablemembrane and discharging the fluent material; and (c) electron supplymeans for providing free electrons at said second side of said membraneso that the electrons pass through said membrane and enter the fluentmaterial to provide a net negative charge on the fluent materialdischarged by said fluent material discharge means and so that thedischarged fluent material is dispersed at least partially under theinfluence of said net charge, the apparatus further comprising shieldingmeans for blocking transmission of radiation from the vicinity of saidelectron-permeable membrane.
 20. Apparatus as claimed in claim 19,wherein said fluent material discharge means includes a body defining apassageway having a downstream end and means for advancing the fluentmaterial within said passageway to said downstream end, saidelectron-permeable membrane confronting said passageway upstream of saiddownstream end, said shielding means including at least one baffledisposed in said passageway between said electron-permeable membrane andsaid downstream end of said passageway.
 21. Apparatus as claimed inclaim 20, wherein said at least one baffle includes at least one wallsection of said body bounding said passageway and defining atortuous-path section in said passageway between said electron-permeablemembrane and said downstream end.
 22. Apparatus for dispersing a fluentmaterial comprising:(a) an electron-permeable membrane having a firstside and a second side; (b) fluent material discharge means for passingfluent material to be dispersed past said first side of saidelectron-permeable membrane and discharging the fluent material; and (c)electron supply means for providing free electrons at said second sideof said membrane so that the electrons pass through said membrane andenter the fluent material to provide a net negative charge on the fluentmaterial discharged by said fluent material discharge means and so thatthe discharged fluent material is dispersed at least partially under theinfluence of said net charge, the apparatus further comprising anelectrode disposed adjacent said first side of said electron-permeablemembrane so that fluent material passed by said membrane by saiddischarge means will contact said electrode and means for maintainingsaid electrode at a relatively negative electrical potential forattracting positively charged particles from the fluent material. 23.Apparatus as claimed in claim 22, wherein said fluent material dischargemeans includes a body defining a passageway having a section forming aventuri, and wherein said electron-permeable membrane and said electrodeis disposed adjacent said section.
 24. Apparatus as claimed in claim 22,wherein said fluent material discharge means includes a body defining apassageway having a discharge orifice, and wherein saidelectron-permeable membrane and said electrode is disposed adjacent saiddischarge orifice.
 25. Apparatus for dispersing a fluent materialcomprising:(a) an electron-permeable membrane having a first side and asecond side; (b) fluent material discharge means for passing fluentmaterial to be dispersed past said first side of said electron-permeablemembrane and discharging the fluent material; and (c) electron supplymeans for providing free electrons at said second side of said membraneso that the electrons pass through said membrane and enter the fluentmaterial to provide a net negative charge on the fluent materialdischarged by said fluent material discharge means and so that thedischarged fluent material is dispersed at least partially under theinfluence of said net charge, the apparatus further comprising means forvarying with time the quantity of said electrons provided at said secondside of said electron-permeable membrane.
 26. Apparatus as claimed inclaim 25, wherein said electron supply means comprise an electron gunand wherein said means for varying the quantity of said electronscomprises means for varying the quantity of electrons emitted by saidgun.
 27. Apparatus as claimed in claim 26, wherein said electron guncomprises a cathode, a grid and one or more anodes, and wherein saidmeans for varying the quantity of said electrons comprises means forvarying the voltage between the grid and cathode.
 28. Apparatus asclaimed in claim 25, further comprising a device for receiving saiddischarged fluent material, said device being constructed and arrangedto operate cyclically, and wherein said means for varying with time thequantity of said electrons comprises means for varying said quantity insynchronization with said cyclic operation of said device.
 29. Apparatusas claimed in claim 28, wherein said device is an internal combustionengine.
 30. A method of dispersing a fluent material comprising thesteps of:(a) passing a fluent material to be dispersed past a first sideof an electron-permeable membrane and discharging the fluent material;(b) supplying electrons on a second, opposite side of said membrane sothat the electrons pass through the membrane and enter the fluentmaterial so as to provide a net charge on the discharged fluentmaterial, whereby the discharged fluent material is dispersed at leastpartially under the influence of said net charge, said discharging stepincluding the step of passing said fluent material through a passagewayhaving a narrow section forming a venturi so that pressure of the fluentmaterial is reduced below the pressure of the fluent material in otherregions of the passageway as the fluent material passes through saidsection, said electron-permeable membrane being disposed adjacent saidsection, and wherein said step of supplying electrons includes the stepof directing an electron beam at said electron-permeable membrane sothat said beam impinges upon said fluent material in said section whilethe fluent material is at reduced pressure.
 31. Apparatus for dispersinga fluent material comprising:(a) an electron-permeable membrane having afirst side and a second side; (b) fluent material discharge means forpassing fluent material to be dispersed past said first side of saidelectron-permeable membrane and discharging the fluent material; and (c)electron supply means for providing free electrons at said second sideof said membrane so that the electrons pass through said membrane andenter the fluent material to provide a net negative charge on the fluentmaterial discharged by said fluent material discharge means and so thatthe discharged fluent material is dispersed at least partially under theinfluence of said net charge, said electron-permeable membranecomprising a film consisting essentially of boron nitride, the thicknessof said film being less than about 3 microns.
 32. Apparatus as claimedin claim 31, wherein said electron supply means comprises an electrongun and means for actuating said gun to apply an electron accelerationpotential of less than 30 kV.
 33. Apparatus for dispersing a fluentmaterial comprising:(a) an electron-permeable membrane having a firstside and a second side; (b) fluent material discharge means for passingfluent material to be dispersed past said first side of saidelectron-permeable membrane and discharging the fluent material; and (c)electron supply means for providing free electrons at said second sideof said membrane so that the electrons pass through said membrane andenter the fluent material to provide a net negative charge on the fluentmaterial discharged by said fluent material discharge means and so thatthe discharged fluent material is dispersed at least partially under theinfluence of said net charge, wherein said fluent material is a liquidand said fluent material discharge means comprises means for imparting agaseous phase to said liquid before said liquid passes saidelectron-permeable membrane.
 34. Apparatus as claimed in claim 33,wherein said means for imparting comprises means for initially atomizingsaid liquid before said liquid passes said electron-permeable so thatmembrane electrons supplied by said electron supply means enter saidinitially atomized liquid and said initially atomized liquid is furtheratomized under the influence of said net charge.
 35. Apparatus fordispersing a fluent material, comprising:(a) means for supplying saidmaterial; (b) means for injecting electrons into said material so thatthe electrons enter the fluent material to provide a net negative chargeon the fluent material and so that the fluent material is dispersed atleast partially under the influence of mutual repellence of said netcharge; (c) a device for receiving said dispersed material, said devicebeing constructed and arranged to operate cyclically; and (d) means forvarying the quantity of said electrons injected into said material insynchronization with said cyclic operation to thereby vary the extent ofsaid dispersion in synchronization with said cyclic operation of saidreceiving device.
 36. Apparatus as claimed in claim 35, wherein saidmeans for injecting comprise an electron gun, and wherein said means forvarying comprise means for varying the quantity of electrons emitted bysaid gun.
 37. Apparatus as claimed in claim 35, wherein said means forinjecting includes a pair of opposed electrodes and means for applyingdifferent electrical potentials to said opposed electrodes, said meansfor supplying said fluent material including means for passing saidfluent material between said electrodes so that electrons will beinjected into the fluent material under the influence of saidpotentials, said means for varying including means for varying thepotential on at least one of said electrodes.
 38. Apparatus as claimedin claim 35, wherein said device for receiving comprises an internalcombustion engine.
 39. A method of dispersing a fluent materialcomprising the steps of:(a) passing a fluent material to be dispersedpast a first side of an electron-permeable membrane and discharging thefluent material; (b) supplying electrons on a second, opposite side ofsaid membrane so that the electrons pass through the membrane and enterthe fluent material so as to provide a net charge on the dischargedfluent material, whereby the discharged fluent material is dispersed atleast partially under the influence of said net charge, said step ofdischarging said fluent material being conducted so that the staticpressure of said fluent material is subatmospheric as said fluentmaterial passes said electron-permeable membrane.
 40. A method asclaimed in claim 39, wherein said fluent material includes a gaseousphase.
 41. A method as claimed in claim 40, wherein said fluent materialincludes a solid particulate in admixture with said gaseous phase.